To determine the presence or absence of long-term health effects, both harmful and helpful, on infants, children, adolescents, and young adults of specific exposures (chemical, physical, biological, and social) in their environment from preconception to adulthood. [unreadable] To determine the relations and possible effects of environmental exposures on occurrence and severity of specific diseases and conditions of children, such as mental retardation and developmental delay, autism, asthma, delayed sexual maturation, behavior disorders, obesity, and injuries. [unreadable] To asses how genetic variation and other genetic mechanisms for inheritance and expression interact, and how they are modified by environmental factors. [unreadable] To serve as a national resource for future studies of child health and development by providing a rich database and repository of samples and information that can be used to address future questions and hypotheses.